Which backerboard for this?

[DangerMouse]

Hi

I orignially posted this Eeeek Advice appreciated please - https://www.tilersforums.com/threads/eeeek-advice-appreciated-please.99558/

Many thanks for the repies and the advice to mechanically fix backer board instead of plastering first was fab.

I've let the wall air and any damp bits dry, and finally removed the rest of the tiles, any loose skim etc. Yeah I know, could have built a new house in that time



I've researched different boards here, and am erring towards 6mm Delta board, mechanically fixed, with waterproof tape on the joins.
My reasoning being that it won't need tanking.

My questions...

1 - Is that sensible?

2 - Will flexible adhesive be ok filling those bits where the plaster is low? Or do I now need plaster? (I will be mechanically fixing the boards too)

3 - What tape would you guys recommend for the joints?

I really appreaciate you pro's helping a DIYer. Thanks

 

[Joe8189]

Hey Danger mouse,
Looking at the photos, I would start by removing the slivers in the corner. Then prime the walls. There is a lot of contradiction regarding using a PVA primer. I would personally choose a Bal ADP primer its an acrylic primer and less likely to degrade with the adhesive/moisture.
Your choice of board is ok and yes it would be advisable to tank with a self adhesive tape (Aquaseal or similar).
I assume you will tile up to the existing wall tiles?
Once you have primed the wall i would dot and dab the wall with adhesive at uniformed spacing, This will help when you come to hard fix the board, dot and dab means smearing uniformed blobs of adhesive to the wall. This will allieviate the need for any filling of the wall.
Start at the bottom and stick your board to the wall all the way up. Make sure to plumb and square the boards as you go. Then leave to set overnight.
Drill through the boards at the area where the dot and dab was and anchor using the raw plugs and screws.
Apply your tape to the joints and also over the screw heads.
You are then ready to tile.
Regards
Joe

 

[DangerMouse]

Hi Joe
Thanks mate, very helpful.
The slivers are all gone now, and yes I'll re-tile up to the existing tiles on the other wall.
I'm going to put a solid bed under the baords before mechanically fixing. It's not a huge area so I should have plenty of adhesive.
Thanks for the recommendations on primer, and tape!

 

[Dave]

Just to add , there should be no confusion about pva or acrylic primer.
Pva does not and i state not!! Stop any reaction from a cement based adhesive onto a gypsum based substrate .. you need an acrylic primer or even a sbr.
pva allowed to dry and then tiled over will become live again with adhesive wetting it and will result in a fail.

 

[DangerMouse]

Thanks Dave.
PVA seems to be touted as the magic bullet to many construction jobs. I'll use proper primer
cheers

 

[Dave]

Thanks Dave.
PVA seems to be touted as the magic bullet to many construction jobs. I'll use proper primer
cheers

It does ye. Read the pva v primer thread I’ve just bumped.